Removal of wax from hydrocarbon oil



Patented Apr. 16, 1935 1,998,397 7 EMOVAL or WAX FROM H naooAReoN OIL Bernard Y. McCarty, Beacon, N. Y., and William E. Skelton, Cambridge, Mass, assignorsto The Texas 'Company,.-New York, N.,-Y., a corpora tion of Delaware 3 No Drawing.

This invention relates to the removal of wax from hydrocarbons and more particularly to an improved process for the removal of parafiin from lubricating oil fractions derived from petroleum.

The invention contemplates a. process of de- Waxing wax-containing lubricating oil fractions by filtration at low temperatures, wherein the Wax-containing oil is mixed with a wax-precipb tating liquid medium composed of a solvent liquid or mixture of solvent liquids which is completely miscible with, and exerts a substantially complete solvent action upon, the oil at the temperatures at which the wax constituents are precipitated from the oil in solid form'and which has substantially no solvent action on the solid hydrocarbons at such temperatures. The resulting mixture is then chilled to precipitate the solid hydrocarbons which are removed by filtration.

More specifically the invention contemplates mixing with lubricating oil fractions a'wax-precipitating liquid medium composed of a mixture of iso-propyl-ether and a liquid selected from the group comprising ethylene dichloride, propylene dichloride and methyl ethyl ketone.

An object of this invention is to effect dewaxing of parafin-containin'g hydrocarbon oils with an improved type of solvent liquid composed of a mixture of solvents having selective solvent properties between the oil and. the wax constituents and which, in addition, retains its selective solvent properties at relatively low temperatures whereby the precipitation of the wax from the mixture, particularly in the case of mixtures with relatively viscous oils, is eiiected in a more readily filterable form. At the same time, a high yield of dewaxed oil is obtained.

A further object has been to develop a solvent liquid which possessed the foregoing properties at relatively low temperatures and which is, therefore, adaptable for the manufacture of lubricating oils having pour tests of 20 F. and lower.

A selective solvent suitable for the foregoing miscibility is necessary in order to prevent separation of such liquid hydrocarbons from the solution. Such separated liquid hydrocarbons materially increase the viscosity of the solution thereby tending to reduce the filtering rate to a point where the operation is not economical. In addition, the presence of this separated liquid Application November 30, 1931, Serial No. 578,207

6 Claims. ,(Cl. 196-195 gives rise to a condition which is productive upon filtration of a wax cake containing substantial amounts of oil so that the maximum yield cidewaxed oil is not realized. f

It is essential'that such a solvent mixture re;-

peratures and not exhibit any tendency for any PATENT oFFiCE main completely homogeneous at these low ternof its components to separate iromthe mixture.

Upon separation of one of the componentsfrom the solvent mixture, the ratio of the components remaining in the mixture is altered, thereby changing its selective solvent properties so that the wax constituents will not be completely precipitated and/or appreciable amounts of the liquid hydrocarbonmay separate from the solution due to the resulting lack of complete miscibility on the part of the solvent with the oil owing to its altered condition. 1

Extensive investigation has demonstratedthat a solvent liquid or solvent mixture satisfactory. H

for use as a wax-precipitating medium in the de.- waxing of wax-containing hydrocarbon oils must possess, among other things, low absolute viscosity and low viscosity temperature coefficient, high oil solubility at .low temperatures, low wax solubility at low temperatures, low freezing point, and also possess the property of, precipitating wax' in a readily filterable condition. y J

Accordingly, after investigating various solvent liquid mixtures, it had been found that a mixture of iso -propyl-ether and either ethylene dichloride, or propylene dichloride, or methyl ethyl ketone, possesses the foregoing combination of properties, thereby rendering it superior to the solvent liquids or liquid mixtures hitherto used in the art and, therefore, particularly Well adapated as a Waxprecipitating medium for use in the manufacture of low pour test paraflin base lubricating oil. The relative proportion of these liquids to each other,

as well as that of the resulting solvent mixture to the oil, may be varied as desired, depending upon the nature of the oil undergoing treatment.

Thus when dewaxing the lubricating distillate fraction, having a viscosity of around to Saybolt Universal seconds or higher at 210 F., about thirty parts of the oil may be mixed with about seventy parts of a solvent mixture composed of around '70 to 80% of iso-propyl-ether and 30 to 20% propylene dichloride. The resulting mixture is then chilled to about 10 F. or to a temperature corresponding substantially to the desired pour test of the resulting dewaxed oil, following which it is subjected to filtration while still maintained in a cold condition to separate the precipitated wax constituents. Advantageously filtration may be carried out in the presence of a comminuted filter aid material which may be added to and commingled with the mix ture of oil, solvent and suspended wax crystals. After removal of the solvent liquid from the illtrate, the resulting lubricating oil will have a pour test of 0 F. or lower.

Somewhat similar results may be obtained, on the other hand, by mixing the oil in about the same proportion with a solvent mixture composed of about 50% of equal parts of iso-propylether and ethylene dichloride. In the case of methyl ethyl ketone a solvent mixture composed of approximately of iso-propyl ether and 40% of methyl ethyl ketone is advantageous.

While the use of the foregoing solvent liquid mixtures has been described in connection with a lubricating distillate fraction of relatively high viscosity, it is contemplated that mixtures of these solvent liquids may be equally well employed with oils of various viscosity ranges. It is also contemplated that mixtures of these solvent liquids are not necessarily restricted to dewaxing distillate fractions but may also be used in dewaxing various wax-bearing fractions of mineral oil.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

l. The process of dewaxing wax-bearing mineral lubricating oil comprising mixing the oil with a selective solvent mixture composed of isopro-pyl ether and ethylene dichloride in such proportions that the mixture has a selective action as between wax and oil at temperatures of around 0 F. and below, chilling the mixture to solidify the wax, separating the solidified wax, and recovering the solvent from the resulting dewaxed oil.

2. In the process of manufacturing low pour test lubricating oils from wax-bearing mineral oils substantially as described, the step comprising mixing with the oil a selective solvent liquid composed of iso-propyl-ether in admixture with ethylene dichloride in which the iso-propyl-ether is at least equal in volume to the ethylene dichloride.

3. In the process of manufacturing low pour test lubricating oils from wax bearing mineral oils substantially as described, the step comprising mixing with the oil a selective solvent liquid composed of iso-propyl-ether in admixture with propylene dichloride in which the iso-propylether is at least equal in volume to the propylene dichloride.

4. The process of dewaxing wax-bearing mineral lubricating oil comprising mixing the oil with a selective solvent mixture composed of isopropyl ether and proplyene dichloride in such proportions that the mixture has a selective action as between wax and oil at temperatures of around 0 F. and below, chilling the mixture to solidify the wax, separating the solidified wax, and. recovering the solvent from the resulting dewaxed oil.

5. The process of manufacturing lubricating oil having a pour test of 0 F. or lower from waxbearing mineral oil which comprises mixing with the oil a selective solvent liquid composed of isopropyl-ether and a liquid selected from the group consisting of ethylene dichloride and propylene dichloride, the solvent liquid being mixed in such proportion that at temperatures of the order of l0 F., the mixture has substantially complete solvent action on the oil, and substantially no solvent action on the wax, chilling the mixture to a temperature of about 10 F. or lower to precipitate the wax constituents as solid hydrocarbons, and removing the solid hydrocarbons so precipitated.

6. The process of dewaxing wax-bearing mineral lubricating oil comprising mixing the oil with a selective solvent mixture composed of isopropyl ether and a liquid selected from the group consisting of propylene dichloride and ethylene dichloride in such proportions that the mixture has substantially complete selective action as between wax and oil at temperatures of the order of l0 F., chilling the mixture to solidify the wax, filtering the cold mixture in the presence of a filter-aid material to separate the wax, and recoveringthe solvent from the resulting dewaxed filtrate.

BERNARD Y. McCARTY. WILLIAM E. SKELTON. 

